The present application claims priority to Japanese Application No.: 2000-344700, filed Nov. 13, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a magnetic driving pump for a vehicle internal combustion engine. In particular, the present invention is directed to a magnetic driving pump having permanent magnets, which are magnetized to have alternate N poles and S poles around an axial line of a drive shaft and a driven shaft. The permanent magnets are respectively fixed to the drive shaft, which is interlocked with a crankshaft of the engine and the driven shaft, which is coaxially provided with the drive shaft.
2. Description of Background Art
Conventionally, a magnetic driving pump, in which mutually magnetized permanent magnets are respectively fixed to a drive shaft driven by an electric motor and a driven shaft coaxially provided with the drive shaft, is known from, e.g., Japanese Published Unexamined Patent Application No. Sho 64-66490.
However, in this magnetic driving pump, a phase difference between magnetic poles of the permanent magnet on the drive shaft side and the permanent magnet on the driven shaft side increases by a resonance phenomenon due to variations in revolution of the drive shaft side and variations in revolution of the driven shaft side. Accordingly, power is transmitted from the drive shaft side by the magnetic force. Furthermore, the phase difference may exceed a relative angle range of magnetic poles for power transmission between the drive shaft and the driven shaft, and a power-transmittable torque between the drive shaft and the driven shaft may be degraded by degradation of the relative magnetic force. Accordingly, a step out (pull out) phenomenon, wherein the driven shaft side cannot rotate in correspondence with the drive shaft side may occur.
In the magnetic driving pump disclosed in the above Japanese Published Unexamined Patent Application No. Sho 64-66490, an inertial moment of the drive shaft side is set to a value 4 or more times greater than that on the driven shaft side. Accordingly, variations in the revolution on the drive shaft side are suppressed to attain mild acceleration and prevent the occurrence of the pull out phenomenon on the driven shaft side.
However, in a magnetic driving pump, wherein a drive shaft is interlocked with a crankshaft of an internal combustion engine having a wide revolution area, especially an internal combustion engine mounted on a vehicle, the occurrence of the pull out phenomenon on the driven shaft side cannot be completely prevented only by a change in inertial mass as described above.
The present invention has been made in view of the above situation, and has as its object to provide a magnetic driving pump for a vehicle internal combustion engine to reliably prevent the occurrence of the pull out phenomenon.
To attain the foregoing object, according to a first aspect of the present invention, a magnetic driving pump for a vehicle internal combustion engine includes permanent magnets, which are magnetized to have alternate N poles and S poles around an axial line of a drive shaft and a driven shaft. The permanent magnets are respectively fixed to the drive shaft, which is interlocked with a crankshaft of the engine and the driven shaft, which is coaxially provided with the drive shaft of the engine. The permanent magnets are magnetized to have alternate N poles and S poles 90 degrees or 180 degrees in phase in a peripheral direction, and are respectively fixed to the drive shaft and the driven shaft.
According to this construction, 4-pole or 2-pole permanent magnets having different magnetic poles adjacent in a peripheral direction are respectively fixed to the drive shaft and the driven shaft. The driving force can be transmitted between the 4-pole or 2-pole permanent magnets within a range of 90 degrees or 180 degrees of mutual phase difference. As it is apparent from the experimental results shown in FIG. 3, the phase difference between the driven shaft and the drive shaft in use of 4-pole permanent magnets is 60 degrees at the maximum in an anteroposterior direction on one side. Furthermore, there is an allowable phase difference of 30 degrees (=90xe2x88x9260) before the occurrence of the pull out phenomenon. Since the allowable phase difference is sufficient when considering changes in magnetic force due to temperature changes, a relative dimensional error between the permanent magnets upon assembly of the pump, a variation in inertial mass on the driven shaft side, and the width of variations in revolution on the internal combustion engine side, the occurrence of the pull out phenomenon can be reliably prevented. Furthermore, during use of the 2-pole permanent magnets, the pull out phenomenon does not occur before the phase difference on the driving shaft side with respect to the driven shaft side becomes 180 degrees on one side. Since there is a sufficient allowable phase difference, the occurrence of the pull out phenomenon can be reliably prevented as in the case of 4-pole permanent magnets. On the other hand, during use of 6 or more pole permanent magnets, according to the experimental results shown in FIG. 3, there is merely an allowable phase difference of 15 degrees or less on one side before the occurrence of the pull out phenomenon. The allowable phase difference cannot be sufficient to prevent the occurrence of the pull out phenomenon.
According to a second aspect of the present invention, in addition to the construction of the above-described first aspect of the present invention, one ring shaped permanent magnet is provided in the inner perimeter of a cup-shaped rotary member fixed to the drive shaft. Another ring shaped permanent magnets is fixed to the driven shaft in the portion coaxially covered with the rotary member. According to this construction, in comparison with the case where a pair of permanent magnets are provided at an interval in an axial direction, an area in which the respective magnetic poles of one permanent magnet face the other permanent magnet side can be increased, to increase transmission torque by the magnetic force. Furthermore, an impeller or the like provided on the driven shaft side can be provided closer to the rotary member on the drive shaft side in the axial direction. Accordingly, the inertial mass on the driven shaft side can be set to a small value, to increase the response of the driven shaft side and more reliably prevent the occurrence of the pull out phenomenon.
According to a third aspect of the present invention, in addition to the construction of the above-described first and second aspects of the present invention, the drive shaft is a camshaft interlocked and connected with the crankshaft at a deceleration ratio of 1/2. According to this construction, since the number of revolutions of the camshaft is 1/2 of that of the crankshaft, variations in revolution of the drive shaft can be suppressed as much as possible, and the occurrence of the pull out phenomenon can be reduced.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.